1. Field of the Invention
The present invention relates to an organic electroluminescence device, and more particularly, to an active matrix electroluminescence device and a method for fabricating the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for enhancing an electrical characteristic of wires outside of an emissive area of the device.
2. Discussion of the Related Art
An electroluminescence device is being viewed as a next generation flat display device for its characteristics of a wide viewing angle, a high aperture ratio, and a high chromaticity. More specifically, in an organic electroluminescence (EL) device, when an electric charge is injected into an organic luminous layer formed between a hole injection electrode and an electron injection electrode, the electron and the hole are paired to each other generating an exciton, the excited state of which falls to a ground state, thereby emitting light. Thus, the organic electroluminescence device (ELD) can be operated at a lower voltage, as compared to other display devices.
Depending upon the driving method, the organic ELD can be classified into a passivation ELD and an active matrix ELD. The passivation ELD is formed of a transparent electrode on a transparent substrate, an organic electroluminous layer on the transparent electrode, and a cathode electrode on the organic electroluminous layer. The active matrix ELD is formed of a plurality of scan lines and data lines defining a pixel area on a substrate, a switching device electrically connecting the scan lines and the data lines and controlling the electroluminescence device, a transparent electrode (i.e., anode) electrically connected to the switching device and formed in the pixel area on the substrate, an organic electroluminous layer on the transparent electrode, and a metal electrode (i.e., cathode) on the organic electroluminous layer. Unlike the passivation ELD, the active matrix ELD further includes the switching device, which is a thin film transistor (TFT).
In the related art active matrix electroluminescence device, the wires and electrodes outside of emissive area are not covered by a protective layer, but mostly covered by an indium tin oxide (ITO) layer. For example, an ITO layer, which is a pixel electrode, is formed on the wire so as to be in contact with the common electrode (i.e., cathode). Subsequently, the common electrode is formed on the ITO layer.
In the emissive layer, since an organic electroluminous layer is formed between the pixel electrode and the common electrode, an interfacial characteristic between the pixel electrode and the common electrode does not change. However, since the pixel electrode and the common electrode formed on the wires are in direct contact with each other, the interfacial characteristic between the two electrodes change. Therefore, the current flow between the wires and the common electrode is deteriorated, thereby lowering product reliability.